It is possible to notice, in particular in the general field of transportation, that numerous functions are carried out by electric driving units.
Consequently, cables connecting batteries to electric actuators are found in numerous apparatuses such as—non-restrictively—: aircrafts, motor vehicles in particular electric and/or hybrid vehicles, etc.
The presence of harnesses of conductive cables has an impact at two levels.
On the one hand, these cables, being crossed by an electric current, emit an electromagnetic field which is disturbing for their environment. It is also appropriate that these cables are not disturbed by possible electromagnetic fields. In other words, it is appropriate to prevent any signal to escape from the cable and also to prevent any parasitic signal to be added to the signal conveyed by this same cable.
On the other hand, the conductive cables are integrated in an apparatus—aircraft, motor vehicle or the like—and, consequently, may be brought into contact with mechanical members of the concerned apparatus. During operation, vibrations that show friction cycles between the cables and the surrounding members, may be produced; these vibrations may damage the cables.
Hence, the electric cables are protected by sheaths which ensure an electromagnetic shielding and a mechanical protection.
In terms of electromagnetic shielding sheath, there is known, for example, from the document EP 1 348 247, an electromagnetic shielding braid which ensures both an electromagnetic shielding—in the range of 50/60 dB at 30/40 MHz—and quality mechanical protection.
However, the principle of the braid, which is therefore closed on itself, may prohibit some applications thereto. Indeed, the set-up of a shielding braid is performed by introducing an end of the cable in the sheath and then making it slide on the cable.
Thus, the set-up of a sheath on a cable which is installed cannot be done without dismounting the latter.
There are also sheaths called self-closing shielding sheaths. Unlike the braided sheaths, these sheaths are constituted by woven ribbons. The warp threads comprise conductive metal strands in order to ensure the shielding function, whereas the weft threads comprise thermo-formable monofilament strands in order to ensure the self-maintaining function of the tubular-shaped sheath.
Given their open construction, the self-closing woven shielding sheaths present poor performances. Their generally observed effectiveness is in the range of 30 dB at 30/40 MHz, namely an electromagnetic effectiveness deteriorated by about 20 to 30 dB in comparison with a braided sheath, such as described before.
The reason why the conventional self-closing woven sheaths present a low shielding capability mainly lies in the absence of equipotential bonding. In order to overcome this absence, tricks are used to create equipotential bondings.
Thus, it is known to place metal collars, for example, at the ends of the sheath. It is also known to perform ties by metal collars at even intervals. This presents a cost both in equipment and in installation time.
Besides, these self-closing woven sheaths may be relatively heavy, which constitutes a handicap for this type of sheaths in particular for aeronautical applications.
In this technical context, an aim of the invention is to provide a light self-closing fabric presenting an electromagnetic shielding effectiveness close to the values of a braided tubular metal sheath, 50-60 dB at 30/40 MHz.